Gaseous waste products resulting from the burning or combustion of hydrocarbonaceous fuels, such as gasoline and fuel oils, comprise carbon monoxide, hydrocarbons and oxides of nitrogen as products of combustion or incomplete combustion and pose a serious health problem with respect to pollution of the atmosphere. While exhaust gases from other hydrocarbonaceous fuel burning sources such as stationary engines, industrial furnaces, etc., contribute substantially to the air pollution problem, the exhaust gases of automobile internal combustion engines are a principal source of pollution. In recent years, with the increasing number of automobiles, the discharge of waste products therefrom has caused considerable alarm, particularly in urban areas, and the control thereof has become exceedingly important.
Of the various methods which have been proposed, the incorporation of a catalytic converter in the exhaust system holds the most promise of meeting the increasingly rigid standards established by government health agencies. A wide variety of metals and metal oxides, either alone or in combination and supported on a refractory porous carrier material, have been recognized for their ability to catalyze the conversion of carbon monoxide and hydrocarbons.